mAbs label regenerating intestine, secretory cells, and central nervous system in specimens processed using optimized protocols. (A-C) 3F11 labels the intestine in tail fragments regenerating a new head, including anterior regions that remodel (arrow, B) and elongate (arrows, C) at early and intermediate stages of intestinal regeneration, respectively. (D-F) After head amputation, 2D2 labels the regenerating brain, including new neuronal projections (arrows, E), and cell bodies (arrows, F). (G-I) 2C11 labels the regenerating peripharyngeal secretory system in tail fragments, including the first appearance of cell bodies 4 days after amputation (arrows, H), and projections within the pharynx 8 days after amputation (arrow, I). Days after amputation are indicated at left. Anterior is to the left in all panels. Dotted magenta lines indicate approximate boundary between new tissue (left) and old tissue (right). All samples were processed using the optimized protocol for each mAb described in Additional file 5. Scale bars: 100 μm (insets in D-F); 200 μm (all others).